This was a thread developing in the
AOR entry comments that I wanted to move to forums. Here's the (trimmed down) conversation:
Hussein: I use JDownloader to download from fileserve, rapidshare, hotfile, filesonic etc. You know, they have very annoying policy with free users such as lengthy waiting and restricted download data and speed. The best way to deal with it is changing IP which AdvTor can do, but they seem to discover that and give error messages like file not found!
ME: the TOR network is set up so that client sites can run a basic script to block TOR users, as not all sites want anonymous visitors. Its likely those sites detect TOR users and restrict them accordingly.
Hussein: I don't understand why Tor gives a chance to web sites to discover anonymous users, then the whole concept of anonymous browsing is meaningless.
ME: Knowing that you are coming from an anonymous network doesn't mean your identity is exposed. Not every website wants anonymous visitors (they frequently cause problems) and the TOR network has to identify itself to avoid legal challenges. I can go into greater detail about this in forums.
Hussein: Yes, webfork. I need more info please.
Simply put, anonymity is easy to abuse. Something I'm fond of quoting is something
Phil Zimmerman said in an interview: he didn't know how to give away powerful security tools without the bad guys having access to them as well. A lot of people take just a little anonymity and decide it means that they can say whatever horrible thing they want (spam, abuse, troll, etc.) without any repercussions. As a result, the
TOR network is a bit like a river: its difficult to stop the flow, but its easy to seal your site in a water-tight container. Also like a river, its very difficult to know where any individual drop originated from.
By contrast, many botnets exist and offer the ability for criminals and spammers to work without getting blocked by destination sites. As many botnet operators have been prosecuted,
TOR must have a method to "opt-out" of its service to avoid legal challenge. However, because political dissidents
need TOR and similar tools to access sites like the BBC, CNN, ACLU, Amnesty International, etc. destination sites can also set up a "whitelist" so
TOR users so they always have access. Even so, its likely they have a system set up so that posts from the
TOR network are flagged right away to filter spam/jerks.
For more information and background, check out the very well-written
Abuse FAQ.